Recent development and wide spread use of medical image capturing apparatuses for Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) have made it possible to obtain a large volume of high-definition digital images for medical use. Furthermore, medical images already interpreted by doctors who are image interpreters are increasingly accumulated one by one together with the image interpretation reports thereof in Picture Archiving and Communication Systems (PACS). In order to interpret a target image with reference to medical images similar to the target image, a start is made for development of techniques for searching out the similar images (medical images) from already-accumulated past cases.
In general, a doctor performs a plurality of tests and considers the results when making an actual diagnosis. In this situation, needs have been created for similar case searches in which images obtained from different modalities are included or information of time-series changes is included.
Patent Literature 1 discloses an apparatus which performs similar case searches using a plurality of test results. In Patent Literature 1, such similar case searches are performed that satisfy the following three conditions: the same image capturing scheme as in a current target case is used; the same test is performed to obtain information between similar cases; and image features are similar to those of the current target image. In the Patent Literature 1, the tests indicate modalities such as a CT apparatus and an MRI apparatus, and the image capturing schemes indicate image capturing approaches, image capturing conditions, image capturing protocols, and image capturing sequences. In Patent Literature 1, it is possible to narrow down many cases extracted in a test using only one of the current target images into a case having a higher similarity.